1. Field of the Invention
This invention relates to a magnetic head assembly used in a drive unit such as a floppy disk drive and, more particularly, to a magnetic head assembly of the type wherein an arm is supported pivotably by a carriage.
2. Description of the Prior Art
A conventional magnetic head assembly of the above type having such a configuration as shown in FIG. 4 in perspective view and FIG. 5 in partial sectional view is proposed in U.S. Pat. No. 4,323,938.
In FIGS. 4 and 5, 1 is a carriage having a lower magnetic head 2 attached to a tip portion, and 3 is an arm having an upper magnetic head 4 attached to a tip portion, with these magnetic heads 2 and 4 arranged substantially opposite to each other. 5 is a leaf hinge spring whose one end is secured to the carriage 1 by screws 6 with the other end secured to the arm 3 by screws 7, so that the arm 3 is connected pivotably to the carriage 1. 8 is a lifting projection provided on one side of the tip portion of the arm 3. Thus, as this projection 8 is lifted by a lifting mechanism not shown, the arm 3 pivots about its base end portion on the side of the leaf hinge spring 5 and moves upward. 9 is a curved surface formed on the base end portion of the arm 3, which abuts smoothly on the upper surface of the leaf hinge spring 5 in response to pivoting of the arm 3. 10 is a tension spring whose one end is attached via a lock member to the carriage 1 with the other end attached via an adjusting screw 12 to the arm 3. By this tension spring 10 the arm 3 is always pushed elastically against the carriage 1. 13 is a stopper provided on the carriage 1, which restricts the angle of pivot of the arm 3 and prevents excessive upward movement of the same.
As a magnetic disk 14 is inserted into the magnetic head assembly of the foregoing configuration, the lower magnetic head 2 and upper magnetic head 4 hold the magnetic disk 14 therebetween and perform the process of read/write of information, during which process the relative positional relation between the magnetic heads 2 and 4 is maintained by the leaf hinge spring 5. At the time of taking out the magnetic disk 14, the lifting projection 8 of the arm 3 is lifted by the lifting mechanism, whereby the arm 3 pivots about its base end portion and moves upward.
The magnetic head assembly as described above, however, has the defect that a considerable extent of twisting appears on the leaf hinge spring 5 at the time of lifting the arm 3. Specifically, because the arm 3 is lifted by means of the lifting projection 8 provided on one side of the tip portion thereof and has the configuration wherein a circumferential inclination of the arm 3 about the axis thereof is restricted little, the one-sheet leaf hinge spring 5 achieving the hinge function of the arm 3 is twisted when the arm 3 is lifted, with its one side in the widthwise direction ( i.e. the side on which the lifting projection 8 is provided ) held in a raised state. Further, because the arm 3 is moved up and down repeatedly, the useful life of the leaf hinge spring 5 being twisted each time the arm 3 moves up and down is short and the reliability of products is impaired.